Cisco 7609 User Manual

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Cisco 7600 Series Router Cisco IOS Software Configuration Guide—12.1E
78-14064-04
Chapter 32 Configuring PFC QoS
Understanding How PFC QoS Works
2q2t Ports
For 2q2t ports, each transmit queue has two tail-drop thresholds that function as follows:
• Frames with CoS 0, 1, 2, or 3 go to the low-priority transmit queue (queue 1):
– Using transmit queue 1, tail-drop threshold 1, the switch drops frames with CoS 0 or 1 when the
low-priority transmit-queue buffer is 80 percent full.
– Using transmit queue 1, tail-drop threshold 2, the switch drops frames with CoS 2 or 3 when the
low-priority transmit-queue buffer is 100 percent full.
• Frames with CoS 4, 5, 6, or 7 go to the high-priority transmit queue (queue 2):
– Using transmit queue 2, tail-drop threshold 1, the switch drops frames with CoS 4 or 5 when the
high-priority transmit-queue buffer is 80 percent full.
– Using transmit queue 2, tail-drop threshold 2, the switch drops frames with CoS 6 or 7 when the
high-priority transmit-queue buffer is 100 percent full.
1p2q2t Ports
1p2q2t ports have a strict-priority queue and two standard transmit queues. The two standard transmit
queues each have two WRED-drop thresholds.
• Frames with CoS 5 go to the strict-priority transmit queue (queue 3), where the switch drops frames
only when the buffer is 100 percent full.
• Frames with CoS 0, 1, 2, or 3 go to the low-priority standard transmit queue (queue 1):
– Using standard transmit queue 1, WRED-drop threshold 1, the switch drops frames with CoS 0
or 1 when the low-priority transmit-queue buffer is 80 percent full.
– Using standard transmit queue 1, WRED-drop threshold 2, the switch drops frames with CoS 2
or 3 when the low-priority transmit-queue buffer is 100 percent full.
• Frames with CoS 4, 6, or 7 go to the high-priority standard transmit queue (queue 2):
– Using standard transmit queue 2, WRED-drop threshold 1, the switch drops frames with CoS 4
when the high-priority transmit-queue buffer is 80 percent full.
– Using standard transmit queue 2, WRED-drop threshold 2, the switch drops frames with CoS 6
or 7 when the high-priority transmit-queue buffer is 100 percent full.
1p3q1t Ports
1p3q1t ports have a strict-priority queue and three standard transmit queues. The standard transmit
queues each have one WRED-drop threshold and one nonconfigurable tail-drop threshold.
• Frames with CoS 5 go to the strict-priority transmit queue (queue 4), where the switch drops frames
only when the buffer is 100 percent full.
• Frames with CoS 0 and 1 go to the low-priority standard transmit queue (queue 1).
• Frames with CoS 2, 3, or 4 go to the medium-priority standard transmit queue (queue 2).
• Frames with CoS 6 or 7 go to the high-priority standard transmit queue (queue 3).
Note You can configure each standard transmit queue to use both a non-configurable 100 percent
tail-drop threshold and a configurable WRED-drop threshold (see the “Configuring
Standard-Queue Drop Threshold Percentages” section on page 32-54).

Cisco 7609 Specifications

General

Chassis Slots	9
Switch Fabric Capacity	720 Gbps
Power Supply Options	AC or DC
Product Type	Router
Form Factor	Rack-mountable
Supported Line Cards	Various Cisco 7600 Series line cards
Operating System	Cisco IOS
Management	CLI, SNMP
Forwarding Performance	400 Mpps
Maximum Power Consumption	4000 Watts
Redundancy	Yes
Interfaces/Ports	Various, depending on line cards installed